There is a conventional thermal printer, which is provided with a thermal head at positions corresponding to one side and the other side of thermal paper having a thermosensitive layer on both sides, and prints both sides of thermal paper by operating both thermal heads, or prints one side of thermal paper by operating one of the thermal heads (e.g., Jpn. PAT. Appln. KOKAI Publication No. 2001-71569).
In the above thermal printer, when the front end of supplied thermal paper reaches a thermal head, feeding of thermal paper is stopped. In this state, a platen roller is moved to a thermal head, and thermal paper is inserted between the platen roller and thermal head. Feeding of thermal paper is restarted in this state, and a thermal head starts printing.
However, the printing speed is delayed by the time to stop feeding of thermal paper.
Further, a little “displacement” occurs between the position of thermal paper contacting a thermal head at stop of feeding thermal paper, and the print start position on thermal paper at the time of restarting the thermal paper feeding and starting printing. This “displacement” is caused by a play or error in movement of a driving system of each platen roller (e.g., a gear to transmit the power of a motor). This “displacement” causes a stripe-like line on thermal paper in a direction perpendicular to a paper feeding direction. This stripe-like line is called a white line, and greatly deteriorates the print quality.